This invention relates to an apparatus and method for facilitating the installation of one of a range of different cannulas according to a medical practitioner's choice, over an expansible tunneling apparatus.
Devices of the general type disclosed in U.S. Pat. No. 5,496,345, which is owned by the Assignee of the present application and which is incorporated in its entirety herein by reference, have been used to achieve excellent results in actual use and, generally, comprise a tunneling member having an expansible device such as a balloon attached to the tunneling member which can be used for tissue dissection. When the tunneling member is used in its preferred mode, an incision is first made to gain access to a natural tissue plane and the tunneling device is introduced and tunnels a path between layers of tissue lying generally parallel to each other along a natural tissue plane. The balloon is then inflated to dissect tissue along the natural tissue plane and an anatomic working space which did not previously exist is created so that surgical or other medical procedures can be performed. Such procedures are more fully described in U.S. Pat. No. 5,496,345.
However, devices of this type presently in use have a bulky proximal end and a captive cannula assembled distally of this proximal end. In practice therefore, it is not possible to exchange cannulas to obtain alternative features without complete removal of the devices. This risks losing access to working space created since the distal end of the device, which maintains a path to the space, must be removed.
In general, it is an object of the present invention to provide an apparatus and method which allow a choice of cannulas after the working space is created and which is simpler for the medical practitioner to use.